1. Field of the Invention
The present invention relates to power supply apparatuses for electronic units, and more particularly, to a power supply apparatus effective for an electronic unit, having a main power-supply section for driving the electronic unit and a standby power-supply section enabled when the electronic unit is not operating.
2. Description of the Related Art
Each of many electronic units available these days is provided with a receiving section for receiving light modulated, for example, by an infrared ray, is provided with a remote-control function for operating the power supply of the electronic unit by receiving the infrared ray emitted from a remote-control transmitter, and is provided with a power supply for holding data, such as the ON/OFF state of the power supply of the electronic unit, a timer of the electronic unit, and last-operation information, as a standby power supply.
Various standby power supplies are available as follows;
1) Those which use a transformer in a main circuit and output a standby power at a secondary side PA0 2) Those which use a compact standby transformer PA0 3) Those which accumulate electric power for operating a standby circuit, in a power-supply circuit and achieve charging when the accumulated electric power is running out. Standby power supplies 3) have less power consumption than power supplies 1) and 2), but require electric power for charging. PA0 4) Those which accumulate electric power for operating a standby circuit, in a power-supply circuit in the same way as those described in 3), do not achieve charging when the accumulated electric power is running out, and become an operation-impossible state. Standby power supplies 4) do not require electric power at standby, but whether they are on standby cannot be externally determined.
In standby power supplies 1) and 2), since transformers are always energized, much electric power is consumed at standby.